(1) Field of the Invention
Subject invention is related to calibration of optical systems such as autocollimators and more particularly to a small angle generating system for deviating or deflecting light beams.
(2) Description of the Prior Art
The angular deflections of light beams have been accomplished in the past by converting large mechanical movements into corresponding small movements of reflecting or refracting surfaces in order to obtain a high optical advantage. However, such methods have been expensive in order to obtain accurate mechanical movements which are repeatable. Furthermore, any nonlinearity in the mechanical movements makes the calibration of the devices difficult. One novel technique to accomplish this is described and claimed in our copending application Ser. No. 07/215,200 filed July 5, 1988. That technique makes use of an optical wedge of small apex angle .alpha. which is rotated to produce a small deviation of a collimated optical beam. However, in case of a rotating optical wedge there are spurious images due to back and forth reflections from the faces of the wedge which give rise to noisy signals. Furthermore, an extended spectral range for a small angle generating system will require several optical wedges with transmission for each wedge in a particular portion of the spectrum. Additionally, there is chromatic dispersion and variable attenuation with wavelength of the wedge. It is thus desirable to have a small angle generating system which is free of the above-mentioned disadvantages.